When doing splits in the spring, I always make certain that Drones are present. As soon as they appear, I am confident that once a new Queen hatches and makes her mating flight, that all will go well. I figure that if Drones are not yet active in my hives, they will probably not be around in other hives either.
So, regardless of what zone you live in, the appearance of Drones in Spring should be a good signal to do your walkaway splints. Here in my part of Texas, usually I do my splits in April or May, depending on how lazy I am.
